Patent GB-279566-A (GB)
Title: Improvements in automatic and semi-automatic telephone circuits
IPC: H04Q3/00
Filed: 1926-07-30
Abstract: 279,566. Standard Telephones & Cables, Ltd., Searle, A. M., Wright, E. P. G., and Baker, J. H. E. July 30, 1926. Automatic exchange systems.-In a system comprising six small exchanges arranged in a chain and each containing less than 100 lines, a connector, Fig. 1, directly accessible from a calling subscriber's line switch, takes into use a register-controller of the code-translating type, Fig. 2, to which the single digit denoting the wanted exchange is transmitted and is there recorded on a register AD. If this digit denotes a local connection, the register-controller is immediately released and the remaining two digits operate the connector in the usual manner to complete the connection to a local subscriber. If, on the other hand, the first digit denotes a connection to another exchange, the registercontroller is held but the two numerical digits pass to the vertical and rotary magnets of the connector as before and are there stored. Only two outgoing junctions J1, J2 are provided for inter-exchange calls and during the dialling of the final digit an idle one of these junctions is seized and a routing member (of from one to four digits) according to the setting of the register AD is then sent out. This is followed bv the retransmission of the numerical digits which is effected by the register-controller in accordance with the setting of the connector, an extra wiper and bank P2 of which is wired to the banks of the register-controller sending switch SSA, SSB. When the register-controller has recorded the first digit, a test is made as to the operative condition of the interrupter springs LS, MS, and if either of these is faulty, the registercontroller is released, the seizure of an outgoing junction is prevented and a busy signal is sent to the calling subscriber. The arrangement shown in the drawing is for a terminal exchange of the chain. For intermediate exchanges, the outlets J1, J2 lead to outgoing group selectors. Local call. When a connector, Fig. 1, is seized, relays A, B operate and ground the starting wire SW. Only two register-controllers are provided and it will be assumed that the one shown in Fig. 2 is idle. Earth on wire SW will therefore operate relay U (unless the call-finder asociated with the other register-controller is at that moment hunting in which case relay UB will be operated). Relay U connects up the stepping magnet DM of the finder PR1 - - PU and hunting takes place until the switch is reached in which earth has been removed from terminal PR1. Relays S, T, then operate in series over wiper PR1. The first digit is repeated by relay A over the circuit B9, N8, C, BC14, T3IPU to magnet ADM. Relay C energizing in this circuit partially energizes two-step relay BC which at the end of the digit pulls up completely. If this digit denotes a local connection, e.g. the digit 7, wiper AD1 completes a circuit for relav CO which releases relays S, T, restoring the register-controller to normal, and resulting also in the release of relay BC. The impulses of the second digit are repeated over contacts B9, N8, C, BC14, T31 to the vertical magnet V and at the end of the digit the relapse of relay C causes the final digit to pass to the rotary magnet R. The busy-test, ringing and release operations take place in known manner. Call to distant exchange; registration of number and seizure of idle junction. If the first digit does not indicate a local call, the registercontroller is held, relays T, BC remain operated, and the second digit passes over front contacts 14, 16 of relay BC to the vertical magnet V and the final digit as before to the rotary magnet R. During the receipt of this final digit, relay E closes a circuit over lead PR2 for relay L which locks up. Relay L places earth on wiper PU which is extended over contacts T31, BC11 to the windings of relays J, K. If the trunk J1 is idle. relay J operates, locks over its upper winding and opens a chain circuit to resistance YC and battery to mark the trunk busy to other switches. If the trunk J1 is busy, the earth from wiper PU is extended over contact J7 to relay K associated with the trunk J2 and if this trunk also is busy, relay G operates and transmits a busy signal to the calling subscriber. Transmission of impulses from registercontroller. When relay S2 falls back at the end of the first digit, it connects springs LS in series with the lower winding of two-step relay LC over a circuit including contacts COS, S9, and wiper AD1. When springs LS have closed and reopened, relay LC operates completely and connects up the upper winding of a second two-step relay CC which in a similar manner operates completely in response to a closing and opening of springs MS. Relay CC completes a circuit over wiper SC1 for moving control switch SC into its 2nd position in which relay CC is released and a further circuit is completed over wiper SC2 and contacts 6 of relay LB in the other register-controller (provided that the latter is not sending impulses) for moving switch JC into position 3. Relay CC now operates again over wiper SC3 and connects springs MS to magnets SSAM, SSBM of the two sending- switches SSA, SSB, which are thus stepped round in synchronism. If one routing digit is to be sent out, the apropriate contact in the bank of wiper AD2 is jumpered to a contact in the first quadrant of any bank of either sending switch, whilst the corresponding contacts in the banks of wipers AD3, AD4 are jumpered to terminals DCO, SDCO, respectively. As soon as the sending switches move from normal, relay SA operates to remove a short-circuit from springs LS so that subsequent openings of these springs cause impulses to be transmitted over wipers +D,-D, and leads +J1,-J1. When the sending switches reach the marked contact, relay SZ operates over wipers AD2, SC2 to short-circuit springs LS, and relay CC is released and closes restoring circuits for the sending switches which come to rest on intermediate (the 13th) contacts. The release of relay SA steps switch LC to position 4 in which parallel circuits SC2, LC8, SSB1, and SC2, SA6, LC11, SSA1 are closed for starting the sending switches over the second quadrant and for energizing relay SA. When the sending switches reach normal, switch SC moves to position 5 in which a circuit over wipers SG2, AD3, terminal DCO and wiper SC1 moves switch SC into position 7. A circuit is now completed over wipers SC2, AD4 and terminal SDCO for causing the sending switches to make another revolution in order to provide time for the numerical digits to be completely registered. When these switches again reach normal switch SC moves to position 9 and in positions 9 and 10 numerical impulses corresponding to the setting of the connector, Fig. 1, are sent out, the bank of wiper P2 being jumpered to terminals in the first and second quadrant of a bank of a sending switch, whilst wiper P2 is connected to wiper SC2 over contacts T7, wiper PR2 and contact S17. At the end of these operations, switch SC moves to position 11 in which relay CO energizes over wiper SC2, releases relays S, T and restores the register-controller to normal. If two routing digits are to be sent out, terminals in the banks of wipers AD2, AD4 are jumpered to the first quadrants of banks of the sending switches and the bank of wiper AD3 is jumpered to terminal DCO. For three routing digits, bank AD2 is jumpered to a first quadrant of a sending-switch bank, bank AD3 to both first and second quadrants and bank AD4 to terminal SDCO. For four routing digits, banks AD2, AD3, AD4 are connected, resepectively, to a first quadrant, a first and a second quadrant, and a first quadrant of the sending switch. Faulty interrupter-springs. If either of the springs LS, MS do not open or close correctly, switch SC does not move out of position 1 and when relay L operates, earth is extended over wiper SC2 and lead PABC to short-circuit relays J, K thus preventing the seizure of an outgoing trunk, whilst earth over PU partially operates the two-step busy relay G. The earth on wiper SC2 also operates relay CO which releases relays S, T, the latter opening the initial circuit of relay G which thereupon operates completely and gives a busy tone. Wiper SC3 closes an alarm circuit AL.